1// Copyright 2013 The Go Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style
3// license that can be found in the LICENSE file.
4
5// This file implements sysSocket and accept for platforms that
6// provide a fast path for setting SetNonblock and CloseOnExec.
7
8// +build dragonfly freebsd hurd illumos linux netbsd openbsd
9
10package poll
11
12import "syscall"
13
14// Wrapper around the accept system call that marks the returned file
15// descriptor as nonblocking and close-on-exec.
16func accept(s int) (int, syscall.Sockaddr, string, error) {
17	ns, sa, err := Accept4Func(s, syscall.SOCK_NONBLOCK|syscall.SOCK_CLOEXEC)
18	// On Linux the accept4 system call was introduced in 2.6.28
19	// kernel and on FreeBSD it was introduced in 10 kernel. If we
20	// get an ENOSYS error on both Linux and FreeBSD, or EINVAL
21	// error on Linux, fall back to using accept.
22	switch err {
23	case nil:
24		return ns, sa, "", nil
25	default: // errors other than the ones listed
26		return -1, sa, "accept4", err
27	case syscall.ENOSYS: // syscall missing
28	case syscall.EINVAL: // some Linux use this instead of ENOSYS
29	case syscall.EACCES: // some Linux use this instead of ENOSYS
30	case syscall.EFAULT: // some Linux use this instead of ENOSYS
31	}
32
33	// See ../syscall/exec_unix.go for description of ForkLock.
34	// It is probably okay to hold the lock across syscall.Accept
35	// because we have put fd.sysfd into non-blocking mode.
36	// However, a call to the File method will put it back into
37	// blocking mode. We can't take that risk, so no use of ForkLock here.
38	ns, sa, err = AcceptFunc(s)
39	if err == nil {
40		syscall.CloseOnExec(ns)
41	}
42	if err != nil {
43		return -1, nil, "accept", err
44	}
45	if err = syscall.SetNonblock(ns, true); err != nil {
46		CloseFunc(ns)
47		return -1, nil, "setnonblock", err
48	}
49	return ns, sa, "", nil
50}
51